Variable radio aerial



Dec. 3, 1940. A. c, DUCATI VARIABLE RADIO AERIAL Filed Oct. 14, 1939Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE Application October14, 1939, Serial No. 299,548

' In Italy October 15, 1938 8 Claims.

This invention relates to aerials for radio communications of thevariable length type for transmitting and receiving on different wavelengths and, more particularly, to aerials constituted by a column ofliquid metal the'height of which may be varied by pneumatic means.

The primary object of the invention is to provide a supporting tube forthe liquid metalv column, which is made up of a plurality of annularsections of alternatingly conducting and insulating material. With thisarrangement, the metallic tubular sections serve for cooling the liquidmetal and act as condenser elements connected in series, so that as theliquid conductor 1 rises in the supporting tube coming into contact withthe metallic parts of the tube, the operating conditions of the aerialare improved.

A further object of the invention is to provide an aerial comprising afixed portion and an ad'- justable portion, the latter consisting of aliquid metal column supported by a tube formed by metallic annularsections alternating with annular sections of insulating material.

Further objects and advantages will appear from the followingdescription in which reference is made to the accompanying drawing,wherein:

Figure l is an elevation of an aerial, of which the supporting tube isformed by a plurality of alternatingly insulating and metallic sections.

Figure 2 shows an aerial comprising a fixed portion and an adjustableportion.

Figures 3 and 4 show two types of joints for the aerials.

Referring to Figure 1, the tube enclosing the mercury column has anentirely metallic or insulating base portion 56 on which are alternatelypiled insulating and metallic tubular elements 57, 58, respectively,tightly sealed together. The tube is broken at an intermediate point inthe drawing to show the tubular structure through which the liquidconductor forming the column 59 flows. The liquid is delivered from thesump Mi by means of the pressure fluid conveyed by pipe 6!.

Figure 2 shows diagrammatically and by way of example one of the variousmanners of carrying out this invention. A tower antenna 62 has attachedthereto the aerial 55, El, 58 having at its lower end the sump 63, fromwhich the pressure pipe (i i extends and delivers pressure for movingthe column of the electric liquid conductor. Pressure is supplied by thesource of 55 pressure 65 and controlled by the pressure gauge 66, thatmay also directly indicate the length as adjusted.

The function of the device is in this case to correct the main aerial62.

Figure 3 showsan example of a tight flanged joint 61 between the tubes51 and 58 which, as said above, are insulating and metallic,respectively.

Figure 4 shows an example of a tight joint between the same tubes 5T and58 employing set 10 nuts 68 and 69, a bush l0 and resilient packings Hand 12.

It will be understood that the tube joints and length and the types ofmaterials employed may be varied at will. The insulating tubes may be 15made in the form of hose, such as rubber hose, or of material having alow dielectric loss, as porcelain, as the case may be.

It should further be noted that with regard to capacitive effects, theposition of all these tubes 20 may be compared with that of condenserelements connected in series, and this feature should be taken intoaccount in determining the length of tubesconstituting the aerial lead,and the height above the sump of this composite portion of the aeriallead.

It should further be understood that a metal other than mercury, whichis liquid at room temperature, such as caesium, or an alloy, such as asodium and potassium alloy, may be used, 30 provided it has thenecessary electric properties. When the last mentioned substances areemployed the tube should be well closed at the top to prevent the accessof moisture to the alloy.

It should finally be understood that the tubular metallic elements maybe utilized for cooling the conducting liquid flowing therethrough, forwhich purpose these elements as well as the insulating elements shall beprovided with ribs or fins for a more efiicient cooling, when this isdesired or useful.

What I claim is:

1. An aerial for radio communications comprising, a column of a metal ina liquid condition, and a supporting tube for said column constituted bytubular metallic sections alternating with tubular sections ofinsulating material.

2. An aerial for radio communications comprising, a tubular bodyconstituted by tubular metallic sections alternating with tubularsections of insulating material, a sump into which said tubular bodydips, a metal in a liquid condition in said sump and in said tubularbody, and pneumatic means acting on the surface of the 55 liquid metalin said sump for adjusting the level of said liquid metal in saidtubular body.

3. An aerial for radio communications comprising, a sump, a tubular bodyformed by a metallic base portion dipping into said sump, tubularmetallic sections alternating with tubular insulating sections on saidbase portions, a metal in a liquid condition in said sump and in saidtubular body, and pneumatic means acting on the surface of the liquidmetal in said sump for adjusting the level of said liquid metal in saidtubular body.

4. An aerial for radio communications comprising, a fixed aerialportion, an adjustable aerial portion formed by a column of a metal in aliquid condition and by a supporting tube for said column made up bytubular metallic sections alternating with tubular sections ofinsulating material.

5. An aerial for radio communications comprising, a tower aerial, a sumpat the upper end of said tower, an annular body constituted by metallictubular sections alternating with tubular sections of insulatingmaterial and dipping into said sump, a metal in a liquid condition insaid sump and in said tubular body, and penumatic means acting on thesurface of the liquid metal in said sump for adjusting the level of saidliquid metal in said tubular body.

6. An aerial for radio communications comprising, a tubular memberformed by tubular metallic sections alternating with tubular sections ofinsulating material, joints for sealing together said tubular elementsin a liquid-tight manner, a column of metal in a liquid condition insaid tubular body, and means for varying the length of said column.

'7. An aerial for radio communications as claimed in claim 1, in whichcaesium is used as metal in a liquid condition.

8. An aerial for radio communications as claimed in claim 1, in which asodium-potassium alloy is used as a metal in a liquid condition.

ADRIANO CAVALIERI DUCATI.

